bug#57693: 29.0.50; Is there a more reliable version of `char-displayable-p'?

[Ihor Radchenko <yantar92@gmail.com>]

Robert Pluim <rpluim@gmail.com> writes:

> Iʼd look at the guts of `describe-char-display' in
> "lisp/descr-text.el" for inspiration (or even use it as is). It takes
> a `pos' argument so you may have to wrap it in `with-temp-buffer' +
> `insert'.

`with-temp-buffer' is not a good option because it may have different
buffer-local environment compared to the actual buffer.

As for `describe-char-display', do you refer to `internal-char-font'?
`internal-char-font' is "For internal use only." though. Or can we get
something out of the `describe-char-display' return value? This function
does not have a docstring, and it is not very clear what the possible
return values can be and which return values are indicative of
non-displayable characters.

-- 
Ihor Radchenko,
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